FIG. 14 is a block diagram of a conventional inertial sensor. As shown in FIG. 14, conventional inertial sensor 130 includes oscillator 131, drive unit 132, and sensing unit 133. Oscillator 131 includes monitoring electrode 131a, driving electrodes 131e and 131c, and sensing electrodes 131b and 131d. Drive unit 132 receives a signal from monitoring electrode 131a, and amplifies and supplies the signal to driving electrodes 131e and 131c. Sensing unit 133 detects the amount of inertia applied from an external source to oscillator 131 based on signals received from sensing electrodes 131b and 131d. 
Sensing unit 133 includes oscillating device 135f, switch 135e, current/voltage converters 135c and 135d, differential amplifier 135g, wave detecting device 135h, and failure diagnosis unit 135j. Switch 135e is connected to oscillating device 135f. Current/voltage converter 135c is connected to sensing electrode 131d and switch 135e. Current/voltage converter 135d is connected to sensing electrode 131b. Differential amplifier 135g is connected to current/voltage converters 135c and 135d. 
Wave detecting device 135h outputs the amount of inertia applied to oscillator 131 based on a signal from differential amplifier 135g. Failure diagnosis unit 135j diagnoses a failure based on a signal from wave detecting device 135h. 
In inertial sensor 130, failures are diagnosed by making oscillating device 135f output an oscillation signal to switch 135e and by making failure diagnosis unit 135j monitor the value of a variable DC.
The conventional inertial sensor, however, cannot diagnose failures that have occurred in the drive unit or the oscillator. Moreover, the inertial sensor cannot detect the amount of inertia during failure diagnosis.
An example of a conventional technique related to the present invention is shown in Patent Literature 1.